Are there any experiments which shows a force on a beam of charged particles, in a magnetic field, including

the effect of reversing (1) the current, (2) the direction of the field?

I remember one we did at school. It had an electron gun in a big round bulb about 6" across, probably with a small amount of gas in it because the electron beam glowed. There was a pair of Helmholtz coils either side to bend the beam. I think it was for measuring the mass of the electron. You'd measure the radius of curvature with a travelling microscope and calculate the field from the current in the coils.

You could certainly adjust the magnetic field direction and intensity, and the electron beam velocity, but you could not reverse the current (that would require emitting positrons not electrons)

Sure. Use an oscilloscope. You can vary the fields (direction and strength), reverse currents, and actually measure the deflections of the beam on the scope.

I am so clever that sometimes I dont understand a single word of what I am saying